The principal objective of this study is to elucidate metabolic functions of polyunsaturated fatty acids and phospholipids in nervous tissues with particular reference to their modulation by ethanol. Our studies focused on the major polyunsaturate of brain, docosahexaenoic acid (22:6n3) and to a lesser extent, on arachidonic acid (20:4n6). Two aspects were studied: i) oxygenation of polyunsaturates in brain. ii) non-oxidative metabolism of polyunsaturated fatty acids to the corresponding ethyl esters. Progress has been made in characterizing hydroxy forms of both 22:6n3 and 20:4n6 formed by rat brain with the aid of reference compounds which were prepared by autooxidation or reaction with soybean, potato or platelet lipoxygenases. Based upon the inhibitor profile and their stereochemical purity it is suggested that peroxidation but not lipoxygenation was the major mechanism of their formation in brain parenchyma. Brain microvessels showed 12-lipoxygenase activity although the level of production was low. During the course of this study, new techniques were developed in analyzing lipoxygenase and autooxidized products: i) Thermospray LC/MS analysis of hydroperoxy-derivatives provided information regarding the position gf oxygenation. ii) Thermospray analysis of leukotrienes in negative ion mode as pentaflurobenzyl derivatives provided a sensitive technique for measurement of the level of leukotrienes in liological samples. iii) A chiral phase HPLC system was established for analysis of the stereochemical distribution of hydroxy derivatives for various polyunsaturated fatty acids. Ethyl ester formation was examined in rat brain in the presence of alcohol primarily from 22:6n3 since this fatty acid is highly localized in brain tissue. As has been shown for other fatty acids, 22:6n3 was transformed to the ethyl ester form at a physiological concentration of ethanol. The amount of this production correlated with the ethanol concentration.